Adjustable delay line utilizing magnetostrictive wire lying in grooves in magnetic supporting medium



Jan. 31, 1967 A. A.-MACDONALD 3,302,135

ADJUSTABLE DELAY LINE UTILIZING MAGNETOSTRICTIVE WIRE LYING IN GROOVES IN MAGNETIC SUPPORTING MEDIUM Filed Feb. 10, 1964 2 SheetsSheet 1 INVENTOR.

Jan. 31, 1%? A. AI'MACD-CINALD 3,302,135

ADJUSTABLE DELAY LINE UTILIZING MAGNETOSTRIGTIYE WIRE LYING IN GROOVES IN MAGNETIC SUPPORTING MEDIUM Filed Feb. 10, 1964 2 Sheens-Sheet 2 IN VEN TOR.

United States Patent Ofiice 3,302,135 Patented Jan. 31, 1967 3,302,135 ADJUSTABLE DELAY LINE UTILIZING MAGNE- TOSTRICTIVE WIRE LYING IN GROOVJES 1N MAGNETIC SUPPORTING MEDIUM Angus A. Macdonald, Hinsdale, lll., assignor to Motorola, Inc., Franklin Park, lill., a corporation of Illinois Filed Feb. 10, 1964, Ser. No. 343,521 9 Claims. ((Il. 3333tl) This invention relates to a variable delay line in which the delay is accomplished by propagating a pressure wave in a wire and in particular to a structure for supporting and shielding a relatively long delay line wire.

In many electrical devices it is desirable to delay electrical signals for periods of time longer than feasibleusing purely electrical circuits. One way in which this has been accomplished has been to convert the electrical signal to a pressure wave in a wire by means of a transducer. A second transducer coupled to the wire at a predetermined distance from the first transducer receives the pressure wave and generates an electrical signal therefrom. The distance along the wire between the first and second transducer and the speed of the pressure wave in the wire determine the duration of the time delay.

ture for the delay line Wire can absorb and reflect energy from the pressure wave and a magnetostrictive input transducer can couple energy to the wire at points other than the desired input point. This can cause errors in the delay duration and distortion of the output signal.

Accordingly, it is an object of this invention to provide an improved mounting structure for supporting a delay line wire to minimize energy loss and reflections caused by the mounting structure.

Another object of this invention is to provide an improved mounting structure for supporting a delay line wire and for shielding the wire from energy radiated by the input transducer.

A feature of this invention is the provision of a supporting structure for a delay line wire consisting of a spiral groove formed on the inside surface of a drum formed of a magnetic material, and partially surrounding the delay line wire to form a magnetic shield for the wire.

Another feature of this invention is the provision of a supporting structure for a delay line wire including a member having a groove therein for receiving the wire, with the surfaces of the groove coated with a material to minimize friction, such as Teflon, to reduce reflection and absorption of Waves in the wire.

The invention is illustrated in the drawings, wherein:

FIG. 1 is a drawing of a variable delay line structure;

FIG. 2 is a cross sectional view of the structure shown in FIG. 1 showing the delay line wire supporting structure and the means for moving the input transducer along the delay line wire;

FIG. 3 is an enlarged view illustrating the relationship between the input and output transducers and the delay line wire; and

FIG. 4 is an enlarged view of the delay line wire supporting structure.

In practicing this invention a delay line supporting structure is provided consisting of a hollow cylindrical drum having a spiral rectangular groove cut on the inside. A delay line wire made from a nickel alloy such as Elenvar and having magnetostrictive properties is coiled in the groove to form a helix. An input transducer, consisting of a coil of wire wound around a hollow cylindrical jewel, through which the delay line wire passes, is moved along the inside surface of the drum. As the input transducer is moved along the inside surface of the drum, the delay line wire is removed from the groove, passes through the jewel and is returned. to the groove. Electrical signals coupled to the input transducer cause it to generate a magnetic field which develops a pressure wave in the delay line wire. The pressure wave travels through the delay line wire to a receiving transducer including a piezoelectric crystal which converts the pressure wave to an electrical signal corresponding to the input signal but delayed in time. The distance between the two transducers determines the amount of delay.

The drum, containing the rectangular groove on its inside surface to support the delay line wire, is made of a magnetic material. The sides of the groove thus provide a path of low reluctance to shield the delay line wire remaining in the groove from the magnetic field produced by the input transducer. The groove is also coated with a thin layer of Teflon to reduce the coefiicient of friction between the groove and the wire. The low coefficient of friction of the Teflon layer prevents reflection from bends in the delay line wire and the absorption of energy from the pressure wave.

A delay line incorporating the features of this invention is shown in FIGS. 1 and 2. Similar portions of the two figures have the same identifying numerals. The delay line includes a circular drum 21, having a rectangular spiral groove 20 on the inside surface. A delay line wire 22, formed of a nickel alloy such as Elenvar and having magnetostrictive properties, rests within the groove forming a helix. An end plate 23 is secured to drum 21 and.

supports a threaded rod 27 centrally positioned within drum 211. One end of an arm 26 is threaded on rod 27 while the other end of arm 26 supports a transmitting transducer 24. The pitch of screw 27 is the same as that of groove 20 so that as arm 26 is rotated, the end of arm 26 supporting transducer 24 advances along theinside surface of drum 21 with transducer 24 always opposite grove 20. Arm 26 is rotated by rod 28 which passes through opening 3t? in arm 26. Rod 28 is connected to an external shaft 29 by arm 18. Shaft 29 is mounted on end plate 25 which is secured to drum 21. Rotating shaft 29 causes arm 26 to rotate and move transducer 24 along the surface of drum 21. Transducer 24 is connected to amplifier 39 by cable 4d, slip rings 35 and 37 and cable 38. A piezoelectric receiving transducer 31 is rigidly fixed to wire 22.

An enlarged view of transmitting transducer 24 and receiving transducer 31 is shown in FIG. 3. Transmitting transducer 24 consists of a hollow cylindrical jewel 32 through which delay line Wire 22 passes. Jewel 32 provides a bearing surface for delay line wire 22. A coil of wire is wound around bearing 32 and is coupled to a source of electrical signals by wires 41. An electrical signal applied to the coil of wire 33 generates a magnetic field which develops a pressure wave in delay line wire 22 by means of the magnetostrictive effect. A Inn-metal shield 34 is provided to minimize the external field produced by coil 33.

A receiving transducer consisting of a hollow cylindrical piezoelectric crystal 31 surrounds delay line wire 22. The crystal is mechanically and electrically bonded to delay line wire 22. The pressure wave received by transducer 31 deforms the crystal and thereby produces an output signal. The electrical signal developed by transducer 31 is coupled to an output amplifier by wires 36.

In operation an input signal to be delayed is applied to transmitting transducer 24 from amplifier 39. The signal applied to transducer 24 creates a pressure wave in delay line wire 22 by means of the magnetostrictive effect. This pressure wave is propagated along delay line wire 22 to receiving transducer 31 where it is converted to an output signal, corresponding to the input signal by transducer 31 using the piezoelectric effect. The delay duration between the input and output signals is determined by the length of wire 22 extending between transmitting transducer 24 and receiving transducer 31.

FIG. 4 illustrates an enlarged portion of the drum structure 21. The drum 21 is constructed of a magnetic material such as steel in which is machined rectangular groove 20. Groove 20 is sufliciently large to contain delay line wire 22. The surface of groove 20 and land 19 between the portions of the groove is coated with a thin layer of Teflon 17.

Since the energy imparted to delay line wire 22 by transmitting transducer 24 is at a very low level, it is desirable to minimize the energy loss from delay line wire 22 to its supporting structure groove 20. To accomplish this, the surface of groove 20 and land 19 is coated with a thin layer of Teflon. The Teflon coating has a low coefficient of friction and thus energy is not transferred from the delay line wire to the sides of groove 2ft, which supports wire 22. Also the Teflon layer reduces reflections from the supporting structure which would appear as noise in the output signal from the delay line.

Drum 21 is manufactured from a magnetic material to provide a low reluctance path for a magnetic field. The low reluctance path provided by drum 21 forms a magnetic shield to minimize the coupling of energy from the magnetic field of transmitting transducer 24 to the portion of delay line wire 22 remaining in groove 20,

Thus, a simple delay line structure has been shown in which noise and distortion of the signal to be delayed is reduced by providing a supporting structure of a magnetic material coated with Teflon to shield the delay line wire from external magnetic fields and to reduce reflections from bends in the delay line wire and to minimize energy transfer from the delay line wire to the supporting structure.

I claim:

1. A delay line wherein the delay is established by propagating a stress wave along a wire, said delay line including incombination, a supporting structure of magnetic material having a groove thereon, a wire positioned within said groove, transducer means adapted to be moved along said groove for removing a portion of said wire from said groove, said transducer means generating a magnetic field in response to an electrical signal applied thereto to impart a stress wave to said removed portion of said Wire, said groove being of suflflcient depth to shield said wire therein from said magnetic field, the surface of said groove being coated with material having a low coefficient of friction to minimize reflections and the dissipation of energy of the stress wave.

2. A delay line wherein the delay is established by propagating a stress wave along a wire, said delay line including in combination, a hollow cylinder of magnetic material having a spiral groove on the inside surface thereof, said groove being substantially rectangular in cross section, a wire positioned within and adjacent to the bottom of said groove and forming a helix, transducer means adapted to be moved along said inside surface for removing a portion of the wire from within said groove, said transducer means being further adapted to generate a magnetic field in response to an electric signal applied thereto to impart a stress wave to said removed portion, said groove being of sufficient depth to shield the wire remaining therein from said magnetic field.

3. A delay line wherein the delay is established by propagating a stress wave along a wire; said delay line including in combination, a hollow cylinder of magnetic material having a spiral groove on the inside surface thereof, said groove being substantially rectangular in cross section, a wire positioned within and adjacent to the bottom of said groove and forming a helix, transducer means adapted to be moved along said inside surface for removing a portion of the wire from said groove said transducer means being further adapted to generate a magnetic field in response to an electric signal applied thereto to impart a stress wave to said removed portion, said groove being of sufficient depth to shield the wire remaining therein from said magnetic field, said groove being coated with Teflon to prevent reflections and dissipation of energy of the stress wave.

4. A delay line wherein the delay is established by propagating a stress wave along a wire; said delay line including in combination, a hollow cylinder of magnetic material threaded on the inside surface, a wire positioned between the sides of and adjacent to the roots of said threads and forming a helix, transducer means adapted to be moved along said threaded surface for removing a portion of said wire from said threads, said transducer means generating a magnetic field in response to an electric signal applied thereto to impart a stress wave to said removed portion of said wire, the height of said threads being sufficient to shield the wire remaining therein from said magnetic field, said threaded surface being coated with Teflon to prevent reflections and the dissipation of energy of the stress wave.

5. A delay line wherein the delay is established by propagating a stress Wave along a wire, said delay line including in combination, a supporting structure of magnetic material having a groove thereon, a wire having a first portion positioned within said groove and a second portion, first transducer means coupled to said second portion of the wire and second transducer means coupled to said first portion of the wire, said first transducer means generating a magnetic field in response to an electrical signal applied thereto to impart a stress wave to said wire, said second transducer means being responsive to said stress wave to develop an electrical signal, means coupled to one of said transducer means for moving the same along said wire relative to the other of said transducer means, said groove being of sufficient depth to shield said first portion of the wire therein from said magnetic fields, the surface of said groove being coated with Teflon to minimize reflections and the dissipation of the energy of the stress wave.

6. In a delay line wherein the delay is established by propagating a stress wave along a wire, the combination including, a supporting structure of magnetic material having a groove thereon, a wire having magnetostrictive properties positioned within said groove, said groove being of suflicient depth to provide magnetic shielding for said wire, the surface of said groove being coated with Teflon to minimize reflections and the dissipation of energy of the stress wave.

7. In a delay line wherein the delay is established by propagating a stress wave along a Wire, the combination including, a hollow cylinder of magnetic material threaded on the inside surface, a wire having magnetostrictive properties positioned between the sides of and adjacent to the roots of said threads and forming a helix, the height of said threads being suflicient to provide magnetic shielding for said wire, said threaded surface being coated with Teflon to prevent reflections and the dissipation of energy of the stress wave.

8. In a delay line wherein the delay is established by propagating a stress wave along a wire, the combination including, a hollow cylinder of magnetic material having a spiral groove on the inside surface thereof, said groove being substantially rectangular in cross section, a wire formed of material having magnetostrictive properties positioned within said groove and forming a helix, said groove being of sufficient depth to provide magnetic shielding for said wire.

9. In a delay line wherein the delay is established by propagating a stress wave along a wire, the combination including, a supporting structure of magnetic material having a groove thereon, a wire having a first portion positioned within said groove and a second portion, transducer means coupled to said second portion of said wire, said transducer means generating a magnetic field in response to a signal applied thereto whereby the stress wave is developed in said wire, said groove being of sufiicient depth to effectively shield said first portion of said wire from said magnetic field.

6 References Cited by the Examiner UNITED STATES PATENTS 1,438,753 12/1922 Douglas 338148 2,810,887 10/1957 Ecklund et a1. 333-31 3,020,497 2/1962 Argentieri 333-30 3,119,088 1/1964 Fliegler et a1. 338-148 HERMAN KARL SAALBACH, Primary Examiner.

10 ELI LIEBERMAN, Examiner.

A. R. MORGANSTERN, M. NUSSBAUM,

Assistant Examiners. 

8. IN A DELAY LINE WHEREIN THE DELAY IS ESTABLISHED BY PROPAGATING A STRESS WAVE ALONG A WIRE, THE COMBINATION INCLUDING, A HOLLOW CYLINDER OF MAGNETIC MATERIAL HAVING A SPIRAL GROOVE ON THE INSIDE SURFACE THEREOF, SAID GROOVE BEING SUBSTANTIALLY RECTANGULAR IN CROSS SECTION, A WIRE FORMED OF MATERIAL HAVING MAGNETOSTRICTIVE PROPERTIES POSITIONED WITHIN SAID GROOVE AND FORMING A HELIX, SAID GROOVE BEING OF SUFFICIENT DEPTH TO PROVIDE MAGNETIC SHIELDING FOR SAID WIRE. 